Method for making a negative working, heat-sensitive lithographic printing plate precursor

Abstract

A method for making a heat-sensitive negative-working lithographic printing plate precursor is disclosed comprising the steps of (i) preparing a coating solution comprising hydrophobic thermoplastic polymer particles and a hydrophilic binder; (ii) applying said coating solution on a support having a hydrophilic surface or which is provided with a hydrophilic layer, thereby obtaining an image-recording layer; (iii) drying said image-recording layer; characterized in that said hydrophobic thermoplastic polymer particles have an average particle size in the range from 45 nm to 63 nm, and that the amount of said hydrophobic thermoplastic polymer particles in the image-recording layer is at least 70% by weight relative to the dried image-recording layer.

1. A method for making a heat-sensitive negative-working lithographic printing plate precursor comprising the steps of
 (i) preparing a coating solution comprising hydrophobic thermoplastic polymer particles and a hydrophilic binder; 
 (ii) applying said coating solution on a support having a hydrophilic surface or which is provided with a hydrophilic layer, thereby obtaining an image-recording layer; and 
 (iii) drying said image-recording layer; 
 wherein said hydrophobic thermoplastic polymer particles have an average particle size in the range from 45 nmn to 63 nm, and the amount of said hydrophobic thermoplastic polymer particles in the image-recording layer is at least 70% by weight relative to the weight of the dried image-recording layer. 
 
     
     
       2. The method according to  claim 1  wherein the hydrophobic thermoplastic polymer particles have an average particle size in the range from 45 nm to 55 nm. 
     
     
       3. The method according to  claim 2 , wherein the amount of hydrophobic thermoplastic polymer particles in the image-recording layer is at least 75% by weight relative to the weight of the image-recording layer. 
     
     
       4. The method according to  claim 2 , wherein the amount of hydrophobic thermoplastic polymer particles in the image-recording layer is less than or equal to 85% by weight relative to the weight of the image-recording layer. 
     
     
       5. The method according  claim 2 , wherein the hydrophobic thermoplastic polymer particles comprise polyethylene, poly(vinyl)chloride, polymethyl(meth)acrylate, polyethyl(meth)acrylate, polyvinylidene chloride, poly(meth)acrylonitrile, polyvinylcarbazole, polystyrene or copolymers thereof. 
     
     
       6. The method according to  claim 2 , wherein the hydrophilic binder is soluble in an aqueous developer having a pH≧10. 
     
     
       7. The method according to  claim 2 , wherein the image-recording layer further comprises an infrared absorbing agent in an amount of at least 6% by weight relative to the weight of the image-recording layer. 
     
     
       8. The method according to  claim 2 , wherein the coating further comprises at least one compound which provides a visible image after image-wise exposure and development. 
     
     
       9. The method according to  claim 2 , wherein the coating further comprises at least one compound which provides a visible image after image-wise exposure of the lithographic printing plate precursor but before development. 
     
     
       10. The method according to  claim 1  wherein the amount of hydrophobic thermoplastic polymer particles in the image-recording layer is at least 75% by weight relative to the weight of the image-recording layer. 
     
     
       11. The method according to  claim 1  wherein the amount of hydrophobic thermoplastic polymer particles in the image-recording layer is less than or equal to 85% by weight relative to the weight of the image-recording layer. 
     
     
       12. The method according to  claim 1  wherein the hydrophobic thermoplastic polymer particles comprise polyethylene, poly(vinyl)chloride, polymethyl(meth)acrylate, polyethyl(meth)acrylate, polyvinylidene chloride, poly(meth)acrylonitrile, polyvinylcarbazole, polystyrene or copolymers thereof. 
     
     
       13. The method according to  claim 12  wherein the hydrophobic thermoplastic polymer particles comprise polystyrene or a copolymer comprising polystyrene and poly(meth)acrylonitrile. 
     
     
       14. The method according to  claim 1  wherein the hydrophilic binder is soluble in an aqueous developer having a pH≧10. 
     
     
       15. The method according to  claim 1  wherein the image-recording layer further comprises an infrared absorbing agent in an amount of at least 6% by weight relative to the weight of the image-recording layer. 
     
     
       16. The method according to  claim 1  wherein the coating further comprises at least one compound which provides a visible image after image-wise exposure and development. 
     
     
       17. The method according to  claim 1  wherein the coating further comprises at least one compound which provides a visible image after image-wise exposure of the lithographic printing plate precursor but before development.